Legal or not, large trademark holders like the NFL do have scouts that walk through craft shows with cease and desist orders at the ready. They threaten both the vendor and the show sponsor with court action. Usually that's all it takes for the sponsor to ask the vendor to pack up and leave. Often the sponsor then bars licensed fabrics/images from all future shows. Mission accomplished for the trademark holder.
What it all boils down to is the risk you, personally, are willing to take. You may very well be in the right, but are you ready and willing to spend the time and money to prove it in court? No one here can decide that for you.